var o={a:1};
const num=null
const num1=1
console.log(typeof num)// js底层设计
console.log(o.toString()); //原型对象有
console.log(Object.prototype.isPrototypeOf(o));
console.log(o.hasOwnProperty("a"));
console.log(num.toString());
console.log(Object.prototype.isPrototypeOf(Number))
console.log(Object.prototype.toString.call(num));


